QSerialPort passing received data to GUI [solved]

jarosda

Hi,
current baudrate is 9600 bps, I receive upto 8 B every 10 ms. Baudrate has to be so slow because it requires the target device (low power embedded board with MSP430). One part of qt application should frequently (100 Hz) handle received data and the second part should show data to the user in GUI (here could be refresh rate about 2 Hz as I wrote above). At this moment this proccess (just showing data in GUI) spent 10% of CPU power (AMD Phenom II X4 965, 3,4GHz).
By target device I mean second side of serial line :-).

sierdzio

Ok, then what about firing the QTimer in the slot that handles the "frequent" data (on_readyRead()), so that the GUI gets a call less often?

SGaist

One other thing: is the data to be appended ? Or does it just replace the current values ?

jarosda

To SGaist: The data are prepended in QString (newest data on the first line in multiline string).
To sierdzio: I think so, yes it could be the easiest way. I will try it

I have one another question related to QSerialPort. Does it possible to handle any QSerialPort exception (framing error, buffer overflow.. etc) ? I am asking becouse sometimes when I debugging app the exception is invoked and I think that is caused by serial port.

kuzulis

2 jarosda,

You can try do connect to SerialPortError signal to catch some errors.

But detecting for FramingError, ParityError or BreakConditionError still is not fully implemented. Because it is very difficult (and sometimes impossible) to make a same behavior for different operating systems to detect these errors.

So, at least catching for this errors should be work on Windows, although it is not a fact, please try it and let me know. :)

In general, the overall approach to catch such errors is not yet implemented in the design. Developers can not agree among themselves. Also it is so hard implement on *nix platforms...

tobias.hunger

You can also try to use the serial device in the UI thread directly. The API is asynchronous anyway and communicating between threads requires locking, etc. This overhead can severely slow down your application.

SGaist

Then, you might be interested in using a "QListView":http://qt-project.org/doc/qt-4.8/qlistview.html with a "QStringListModel":http://qt-project.org/doc/qt-4.8/qstringlistmodel.html

jarosda

Guys thank you for posts, the problem wasn't in qserialdevice at all. The cpu looad was caused by offten accessing qtextedit and related operations with qstring. Thanks again, David.

SGaist

Good to see it works !

If you're problem is solved, can you update the thread title so other people may know that you found a solution ?

jarosda

Ok, I'll do it. I didn't know how to close this thread.